Response scheduling for multiple receivers

ABSTRACT

A base station may poll multiple mobile devices with the same multicast poll, and the polled mobile stations may respond separately at different times based on an assigned delay period for each mobile station that was specified in the poll message.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/969,689 titled, “RESPONSE SCHEDULING FOR MULTIPLERECEIVERS,” filed on Oct. 19, 2004 (attorney docket no. P18154X), whichis a continuation-in-part of U.S. patent application Ser. No. 10/740,648titled, “MULTICAST SDMA TRAINING POLLS,” filed Dec. 18, 2003 (attorneydocket no. P18154).

BACKGROUND

Because of the ever-increasing use of wireless devices, the existing RFspectrum is becoming increasingly busy and crowded. As more and moredevices try to share the same communications channels, the use oftraditional communications protocols may cause the existing channels toreach the limits of their capacity, resulting in network congestion,communications delays, and sometimes even loss of service. For example,some communications protocols use a polling technique: a device that hasdata to transmit may wait until it is polled by a base station. Afterbeing given permission to transmit in the form of this poll, the devicemay transmit some or all of the data it has queued up for transmission.This polling technique may prevent multiple devices from trying totransmit at the same time and interfering with each other. However, ifthe responses are short, and numerous devices are being separatelypolled by the base station in this manner, the overhead of this pollingprotocol may use up a significant portion of the bandwidth, resulting ininefficient use of the channel. One technique for reducing the overheadconsumed by this technique is to poll multiple devices in the same poll.However, this technique may create addition problems as multiple devicesrespond to the poll at the same time and thus interfere with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 shows a diagram of a communications network, according to anembodiment of the invention.

FIG. 2 shows a timing diagram of a communications sequence, according toan embodiment of the invention.

FIG. 3 shows a flow chart of a method of operation of a base station,according to an embodiment of the invention.

FIG. 4 shows a flow chart of a method of operation of a mobile device,according to an embodiment of the invention.

FIG. 5 shows a block diagram of a base station, according to anembodiment of the invention.

FIG. 6 shows a block diagram of a mobile device, according to anembodiment of the invention.

FIG. 7 shows a diagram of a communications sequence, according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knownmethods, structures and techniques have not been shown in detail inorder not to obscure an understanding of this description.

References to “one embodiment”, “an embodiment”, “example embodiment”,“various embodiments”, etc., indicate that the embodiment(s) of theinvention so described may include a particular feature, structure, orcharacteristic, but not every embodiment necessarily includes theparticular feature, structure, or characteristic. Further, repeated useof the phrase “in one embodiment” does not necessarily refer to the sameembodiment, although it may.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.Rather, in particular embodiments, “connected” may be used to indicatethat two or more elements are in direct physical or electrical contactwith each other. “Coupled” may mean that two or more elements are eitherin direct physical or electrical contact, or that two or more elementsare not in direct contact with each other but yet still co-operate orinteract with each other.

As used herein, unless otherwise specified the use of the ordinaladjectives “first”, “second”, “third”, etc., to describe a commonobject, merely indicate that different instances of like objects arebeing referred to, and are not intended to imply that the objects sodescribed must be in a given sequence, either temporally, spatially, inranking, or in any other manner.

The term “processor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory. A “computing platform” may comprise one or moreprocessors.

In the context of this document, the term “wireless” and its derivativesmay be used to describe circuits, devices, systems, methods, techniques,communications channels, etc., that may communicate data through the useof modulated electromagnetic radiation through a non-solid medium. Theterm does not imply that the associated devices do not contain anywires, although in some embodiments they might not.

In keeping with common industry terminology, the terms “base station”,“access point”, and “AP” may be used interchangeably herein to describean electronic device that may communicate wirelessly and substantiallysimultaneously with multiple other electronic devices, while the terms“mobile device” and “STA” may be used interchangeably to describe any ofthose multiple other electronic devices, which may have the capabilityto be moved and still communicate, though movement is not a requirement.However, the scope of the invention is not limited to devices that arelabeled with those terms.

In some embodiments of the invention, a base station may poll multiplemobile devices with a single transmission, with the mobile devicesresponding in a specified order after specified delays. A singletransmission addressed to multiple devices may be referred to herein asa ‘multicast’ transmission, although the scope of various embodiments ofthe invention may not be limited to devices described with this term.

FIG. 1 shows a diagram of a communications network that may usemulticast polls, according to an embodiment of the invention. A poll maybe a request for the addressed device(s) to respond by transmittingdata. For each addressed device, the poll may specify a delay for theaddressed device to wait before responding, and the various delays maybe specified by the base station so that the responding devices with notinterfere with one another by transmitting at the same time. Theillustrated embodiment of a network shows an AP 110 that may communicatewith multiple STAs 131-134. Although AP 110 is shown with four antennas120, other embodiments may have other arrangements (e.g., AP 110 mayhave one, two, three, or more than four antennas). Each STA may have atleast one antenna, shown as 121-124, to communicate wirelessly with theAP 110. In some embodiments the STA antenna(s) may be adapted to operateomnidirectionally, but in other embodiments the STA antenna(s) may beadapted to operate directionally. In some embodiments the STAs may be infixed locations, but in other embodiments at least some of the STAs maybe moving during and/or between communications sequences. In someembodiments the AP 110 may be in a fixed location, but in otherembodiments the AP 110 may be moving during and/or betweencommunications sequences.

FIG. 2 shows a timing diagram of a communications sequence, according toan embodiment of the invention. By way of example, the illustratedembodiment shows 5 STAs, labeled STA1 through STA5, but the scope of theinvention is not limited to this quantity. The AP may poll each STA in agroup (e.g., in the illustrated embodiment a group consists ofSTA1-STA5), the poll requesting each of the selected STAs to send aresponse back to the AP. Each response may occur at a different time sothat the responses from multiple STAs do not interfere with each other.In the illustrated embodiment, all five of the relevant STAs are polledin a single transmission by using a multicast transmission for a poll. Amulticast transmission is addressed to multiple specific devices, eachof which is expected to act upon the content of the transmission. Thisis in contrast to the more common singly-addressed transmission(addressed to a single specific device), or a broadcast (which may beintended to be acted upon by any devices able to receive it). In someembodiments the multicast poll may be sent omnidirectionally, so thatall STAs within range may receive the poll, but only those that areaddressed should respond to it, although the invention is not limited inthis respect. Along with its individual address, each addressed STA mayalso receive an individual timing indicator directing the STA to waitfor a particular time duration before responding with a response. In theillustrated embodiment of FIG. 2, the individual timing durations areshown as t₁-t₅ for STA1-STA5, respectively. In some embodiments thetiming indicator may be a simple ranking (e.g., 1, 2, 3, etc.) which theindicated STA may multiply by a time increment to determine how long towait, but other embodiments may use other techniques (e.g., an indicatormay be directly expressed in units of time; t₁ may unspecified butcommonly understood to have a particular value, etc.). The time t_(T)for the responses is shown in FIG. 2 as the time between the responsestart time (T_(ST)) and the response end time (T_(ET)). T_(ST) may beset for any convenient point that is commonly understood by the AP andthe addressed STAs, such as but not limited to the end of the poll.

The determination of which STAs to include in a poll may be determinedby various factors. Each of the STAs may have previously established itspresence with the AP, and may have provided information on its address,mode of wireless communication, possible data rates, etc. These and/orother factors may be considered by the AP in determining which STAs toplace into the same poll group. If the AP does not receive asatisfactory response from a particular STA, that STA may be polledagain (e.g., in another multicast poll with other STAs that may not havebeen included in the first poll).

FIG. 3 shows a flow chart of a method of operation which may beperformed by a base station, according to an embodiment of theinvention. In flow chart 300, a poll group may be formed at 310. Variouscriteria may be used to determine which of the currently available STAsare to be associated with the particular poll group. For example, someSTAs may already be known to be in a sleep mode or otherwise known notto have data to send, and those STAs might be excluded from the pollgroup in favor of other STAs.

After deciding which STAs to include in the group, at 320 the AP mayassign a different time delay for each STA in the group. These timedelays may be in any usable form, e.g., a direct time delay, a quantityof known increments of time, an ordinal ranking which can be multipliedby known increments of time, etc. In some embodiments, the time delaysmay be determined such that each device is allotted the same time torespond as the other devices, but in other embodiments different timedelays may be allotted for each device, depending on various factors.

The time delays may also include time periods that are not expected tocontain transmissions from the addressed devices. For example, the timedelays may include a delay between the end of the poll and the beginningof the first response. This delay may be a short interframe space(SIFS), although various embodiments of the invention may not be limitedin this manner. The time delays may contain a minimum delay time betweenany two consecutive responses, although various embodiments of theinvention may not be limited in this manner. Such ‘no-transmission’delays may be inserted for various reasons, such as allowing time forthe various devices to process received information, transition betweentransmit and receive modes, etc. At 330 a multicast poll may betransmitted, containing the addresses of the STAs being polled, the timedelays for the STAs being polled, and any other information deemeduseful in the poll.

After the poll has been transmitted and the response period has begun,the AP may receive the first response at 340. At 350 the AP may processthe received response and store the processed information for furtherprocessing at a later time. The amount of processing performed at thispoint may vary (e.g., digitizing the signal and storing it for furtherprocessing, calculating parameters, etc.).

If further responses are expected, as indicated at 360, the AP mayreturn to 340 to receive the next response. The loop formed by 340, 350and 360 may continue until all the STAs in the poll group have had timeto respond, at which time this phase may end. If any of the polled STAsdo not respond, or if the received response is not useable for itsintended purpose (e.g., due to corrupted data), that STA may be polledagain at a later time, possibly in another poll group. A maximum numberof retries for such polls may be established, although the scope ofvarious embodiments of the invention is not limited in this respect.

FIG. 4 shows a flow chart of a method of operation which may beperformed by a mobile device, according to an embodiment of theinvention. In flow chart 400, at 410 a multicast poll may be received,containing the address or other identifier of this mobile device. At 420the timing indicator associated with this mobile device may be extractedfrom the multicast poll and a time delay may be determined from thetiming indicator. At 430 the mobile device may wait until the time delaydetermined at 420 has expired. The time delay may be measured from anyfeasible staring point, as previously described. Upon expiration of thetime delay, the mobile device may transmit its own response at 440.

Embodiments of the invention may be implemented in one or a combinationof hardware, firmware, and software. Embodiments of the invention mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by a processing platform to perform theoperations described herein. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine (e.g., a computer). For example, a machine-readable medium mayinclude read only memory (ROM); random access memory (RAM); magneticdisk storage media; optical storage media; flash memory devices;electrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.), andothers.

FIG. 5 shows a block diagram of a base station, according to anembodiment of the invention. Computing platform 550 may include one ormore processors, and at least one of the one or more processors may be adigital signal processor (DSP). In the illustrated embodiment, AP 110has four antennas 120, but other embodiments may have one, two, three,or more than four antennas. For each antenna, base station 110 may havea modulator/demodulator 520, an analog-to-digital converter (ADC) 530,and a digital-to-analog converter (DAC) 540. The combination ofdemodulator-ADC may convert received radio frequency signals from theantenna into digital signals suitable for processing by the computingplatform 550. Similarly, the combination of DAC-modulator may convertdigital signals from the computing platform 550 into radio frequencysignals suitable for transmission through an antenna. Other componentsnot shown may be included in the illustrated blocks as needed, such asbut not limited to amplifiers, filters, oscillators, multiple DACsand/or ADCs where only one is shown, etc.

FIG. 6 shows a block diagram of a mobile device, according to anembodiment of the invention. The illustrated components of mobile device131 may include a computing platform 650, antenna 121,modulator/demodulator 620, ADC 630, and DAC 640 that may be functionallysimilar to those similarly-named components of FIG. 5, but the device ofFIG. 6 is shown with a single antenna/modulator/demodulator/ADC/DACcombination, and the computing platform 650 may perform the operationspreviously described for a mobile device rather than a base station,although various embodiments of the invention are not limited in theserespects.

FIG. 7 shows a diagram of a communications sequence, according to anembodiment of the invention. In the illustrated embodiment, a wirelessdevice (such as a base station, although some embodiments of theinvention may not be limited in this respect) may make a transmissionaddressed to several STAs. Three STAs are shown, but the same principlesmay be used with any feasible number of STAs. The transmission may be inthe form of a Physical layer convergence Protocol Data Unit (PPDU),although some embodiments of the invention may not be limited in thismanner. The transmission may comprise multiple blocks, with each blockaddressed to specific STAs. Each block may be in the form of a Mediumaccess control Protocol Data Unit (MPDU), although some embodiments ofthe invention may not be limited in this manner. In the illustratedembodiment, each block may comprise various information, such as 1) anaddress specifying which STA is being addressed, 2) an offset specifyinghow long after completion of the base station's transmission the STAshould wait before beginning its response, and 3) a duration specifyinghow long the STA has to respond. Each offset and its associatedduration, when combined, may be the equivalent of one of the timeperiods t1, t2, etc., shown in FIG. 2.

The base station may determine the offsets and durations to specify,using various criteria. For example, the first offset may be based on adetermination of how long it might take the addressed STA to recognizeit is being addressed and prepare itself for transmission, as well as adetermination of how long it might take the base station to switch to areceive mode after completing its transmission. In some embodiments thefirst offset may be determined to have a minimum value of somepredefined time period, such as a Short Interframe Space (SIFS). Thefirst duration may be based on various criteria. For example, someembodiments may dictate that the addressed STA must terminate itsresponse within the indicated duration time, even if it has additiondata to send, while other embodiments may use other techniques (e.g.,determining before the poll how much data the STA has to send andspecifying a duration that will accommodate that amount of data). Othertechniques may also be used.

The second offset may be based on the first offset and first duration.In some embodiments, the second offset may be equal to the first offsetplus the first duration. Alternatively, the second offset may be equalto the sum of those two time periods plus additional time. Suchadditional time may be, for example, a defined delay between the end ofthe response from the first STA and the beginning of the response fromthe second STA, although various embodiments of the invention may not belimited in this manner. When included, such additional time may bedetermined in various ways, such as but not limited to the ability ofthe base station to switch from receiving data from one STA to receivingdata from another STA. As before, the second duration may also bedetermined in various ways. In some embodiments, the time to switchbetween receiving data from different STAs may be less than the time toswitch between transmitting and receiving.

In a similar manner, the third offset may comprise the second offsetplus the second duration, and may possibly include additional time aswell, while the third duration may be determined in various ways. Thesesame techniques may be extended to include additional offsets anddurations for additional STAs. In some embodiments the various offsetsmay be determined in different ways (e.g., some offsets may includeadditional time between responses while other do not), and/or thevarious durations may be determined in various ways (e.g., some STAs maybe granted enough time to transmit all queued-up data, while others arelimited to a defined response time without regard to how much data theyhave queued up to send). Some embodiments may use other factors todetermine offsets.

The responses from the STAs may have various formats. For example, insome embodiments the response from a STA may comprise a PPDU, which mayin turn comprise multiple MPDUs, but other embodiments may use othertechniques.

The foregoing description is intended to be illustrative and notlimiting. Variations may occur to those of skill in the art. Thosevariations are intended to be included in the various embodiments of theinvention, which are limited only by the spirit and scope of theappended claims.

1-25. (canceled)
 26. An apparatus, comprising: a first electronic deviceadapted to wirelessly transmit a poll comprising: a first address of asecond electronic device and a first time duration indicator indicatinga transmission time for the second electronic device to transmit a firstresponse to the poll; and a second address of a third electronic deviceand a second time duration indicator indicating a transmission time forthe third electronic device to transmit a second response to the poll.27. The apparatus of claim 26, wherein the poll further comprises afirst time delay indicator indicating a first time delay correspondingto an amount of time for the second device to wait before transmittingthe first response and a second time delay indicator indicating a secondtime delay corresponding to an amount of time for the third electronicdevice to wait before transmitting the second response.
 28. Theapparatus of claim 27, wherein a difference between the first time delayand the second time delay is at least as great as a time for the secondelectronic device to transmit the first response.
 29. The apparatus ofclaim 27, wherein the first time delay is based at least in part upon adetermination of the time taken by the second electronic device toprepare for transmission.
 30. The apparatus of claim 27, wherein thefirst time delay is based at least in part upon the time taken by thefirst electronic device to switch to a receive mode after completingtransmission of the poll.
 31. The apparatus of claim 27, wherein thesecond time delay is based at least in part upon the time taken by thefirst electronic device to switch from receiving data from the secondelectronic device to receiving data from the third electronic device.32. The apparatus of claim 27, wherein the poll comprises a first blockof data containing the first address and the first time delay indicator,and further comprises a second block of data containing the secondaddress and the second time delay indicator.
 33. The apparatus of claim32, wherein the first and second blocks of data are each formatted inaccordance with a medium access control protocol.
 34. The apparatus ofclaim 26, wherein the first electronic device is further adapted tocreate a poll group by assigning the first and second addresses to thepoll group.
 35. The apparatus of claim 26, further comprising multipleantennas, wherein the apparatus is adapted to transmit the poll from atleast one of the antennas.
 36. The apparatus of claim 26, wherein theapparatus comprises a base station.
 37. The apparatus of claim 26,wherein the poll further comprises a delay between an end of the polland a beginning of the first response.
 38. An apparatus comprising: anelectronic device adapted to: receive a poll with multiple addressesincluding a particular address associated with the electronic device,the poll further including a first time duration indicator indicating atransmission time for the electronic device to transmit a response tothe poll; and wirelessly transmit the response to the poll.
 39. Theapparatus of claim 38, wherein the poll comprises multiple blocks ofdata, with each block containing a different one of the multipleaddresses.
 40. The apparatus of claim 39, wherein each of the multipleblocks of data is formatted in accordance with a medium access controlprotocol.
 41. The apparatus of claim 38, wherein the apparatus is amobile wireless device.
 42. The apparatus of claim 38, furthercomprising at least one antenna to transmit the response.
 43. Theapparatus of claim 38, further comprising at least one antenna toreceive the poll.
 44. An article comprising: a machine-readable mediumthat provides instructions, which when executed by a processingplatform, cause the processing platform to perform operationscomprising: transmitting a multicast poll addressed to multipleelectronic devices, the multicast poll containing a respective timeduration indicator indicating a transmission time for each of themultiple addresses to transmit a respective response to the poll; andreceiving the respective response from each of the multiple electronicdevices.
 45. The article of claim 44, wherein the multicast pollcomprises a different time delay indicator for each of the multipleaddresses, and further comprises multiple blocks of data, each blockcomprising one of the addresses and a corresponding time delayindicator.